The main difference between Markovnikov and Anti Markovnikov rule is that Markovnikov rule indicates that hydrogen atoms in an addition reaction are attached to the carbon atom with more hydrogen substitutes whereas Anti Markovnikov rule indicates that hydrogen atoms are attached to the carbon atom with the least …

The addition of HBr (but not of HCl or HI) to unsymmetrical alkenes in the presence of peroxides such as benzoyl peroxide takes place contrary to Markovnikov’s rule. This effect is known as the Kharasch effect.

Markovnikov Rule predicts the regiochemistry of HX addition to unsymmetrically substituted alkenes. The halide component of HX bonds preferentially at the more highly substituted carbon, whereas the hydrogen prefers the carbon which already contains more hydrogens.

Answer: When HBR is added to unsymmetrical alkenes in the presence of peroxide, 1-bromopropane is formed contrary to 2-bromopropane (according to Markovnikov’s rule). This reaction mechanism is known as Anti Markovnikov addition or Kharash effect. It was named after a pioneering organic chemist M. S.

More generally, Zaitsev’s rule predicts that in an elimination reaction, the most substituted product will be the most stable, and therefore the most favored. The rule makes no generalizations about the stereochemistry of the newly formed alkene, but only the regiochemistry of the elimination reaction.

Hofmann’s rule: When an elimination reaction which can produce two or more alkene (or alkyne) products, the product containing the less highly substituted pi bond is major.

Saytzeff’s Rule is also called Zaitsev’s rule, Saytzev’s rule or Z-rule. Based on this analysis, Zaitsev stated that stable alkene is formed when the removal of hydrogen from β-carbon has a low number of hydrogen substituents. During elimination reactions, Saytzeff’s Rule comes into the picture.

According to Saytzeff rule “In dehydrohalogenation reactions, the preferred product is that alkene which has the greater number of alkyl groups attached to the doubly bonded carbon atoms.”

The Hofmann rule states that the major product in Hofmann eliminations and other similar elimination reactions is the less stable alkene (or the alkene featuring a lesser substituted double bond). This rule is used to predict the regio selectivity of some elimination reactions.

The Hofmann Elimination is an elimination reaction of alkylammonium salts that forms C-C double bonds [pi bonds]. In contrast with most elimination reactions that yield alkenes, which follow the Zaitsev (Saytzeff) rule, the Hofmann elimination tends to provide the less substituted alkene.

2. Stability of Alkenes Increases With Increasing Substitution. Since the same bonds are formed and broken in every hydrogenation reaction, the heat of hydrogenation is measuring the stability of each type of alkene. This means that the lower the heat of hydrogenation, the greater the stability of the alkene.

The branching, it seems, means that the electronic structure is simply more compact and this decreases molecular surface area per atom and so leads to a lowering of energy and a concomitant increase in stability.

Now we can return to your question and try to understand why 2-methylpropene is more stable than trans-2-butene. Carbon-hydrogen hyperconjugation is at the center of the answer. Since resonance structure A is more stable than resonance structure B, 2-methylpropene will be more stable than trans-2-butene.

However propene is more stable than 1-butene. This is because there are three hydrogens on α-methyl group involved in hyperconjugation. Whereas, in 1-butene there are only two hydrogen atoms on -CH2 group that can take part in hyperconjugation.

• IMO.
• IEO.
• HBBVS.

The carbon holding negative charge in carbanion comprises one sp3 hybrid orbital that contains a pair of electrons and thus, due to repulsion between the electrons, there is no risk that it will undergo bonding contact with the adjacent C-H bond.

1. Reactant Stability/Reactivity: The more stable the reactant, the less reactive it will be. In terms of rates, this means that the more stable the reactant, the slower it will react.

The stability order of carbanion decreases, while moving from primary to the tertiary anion, due to increase intensity of negative charge on central carbon of tertiary anion.

Generally, the benzylic carbocations are more stable than allylic carbocations as they form more number of resonating structures and have less electron affinity.